The aim of this work was to investigate the MRI findings on tumor xenografts induced in nude mice by the inoculation of human pancreatic cancer cells labeled with superparamagnetic iron oxide (SPIO), and to monitor the kinetics of SPIO distribution in tumor xenografts. The labeled cancer cells were subcutaneously inoculated into 11 nude mice to induce tumor xenograft. The unlabeled cancer cells served as a control inoculated into nine nude mice. MR imaging was performed with a 1.5T MR scanner for the tumor xenograft at the first, second and third week after the inoculation. We found that the tumor xenograft was induced in 100% nude mice on MR imaging for both groups in the first week after the inoculation. In the SPIO group, the tumors showed homogeneous hypointensity on T1- and T2-weighted and FIESTA images 1week after inoculation. Two and 3weeks after inoculation, the center of the tumors was still hypointense on all the above sequences. The tumor periphery was isointense on T1-weighted, and hyperintense on T2-weighted and FIESTA images. The tumors in control group were homogeneously hypointense or isointense on T1-weighted, and hyperintense on T2-weighted and FIESTA images in the first, second and third week after the inoculation. The size and signal-to-noise ratio of the tumor center in the SPIO group had decreased subsequent to the inoculation in all T1- and T2-weighted images and FIESTA. Our results showed the human pancreatic cancer cells labeled with SPIO can induce tumor xenograft in nude mice and MRI can monitor the kinetics of SPIO distribution in tumor xenografts.